Force-measuring apparatus including totalizer means

ABSTRACT

Force-measuring apparatus of the type including electromagnetic compensation means having a movable member that is returned to a no-load position relative to a stationary member by the supply of compensating current pulses of constant amplitude and variable length to a compensation coil secured to said movable member, characterized by the provision of counter means for counting subtotal numbers of counting pulses during periods corresponding with the lengths of said compensating current pulses, respectively, and means including counter control means for periodically transferring to store means the total value of the successive subtotals in the counter means and for simultaneously resetting the counter means to zero. Coarse control means are provided for causing the totalized subtotal pulse count to correspond with a decimal multiple or fraction of a weight unit, and additional store means are provided for optionally indicating for each of a series of subtotal measuring operations the net arithmetic difference between the totalized value and a given pulse reference value (such as tare). According to an alternate embodiment, means including subtotal rate selection switch means are provided for establishing low and high frequency subtotal rates, respectively, and stage selection switch means are operable in conjunction with the operation of said rate switch selection switch means for supplying the counting pulses to corresponding low and high stages, respectively, of the counter.

[ Jan. 22, 1974 FORCE-MEASURING APPARATUS INCLUDING TOTALIZER MEANS [75]Inventor: Heinz Allenspach, Faellenden,

Switzerland 1 Assisnw like!" nstsqms nfiyrish Switzerland [22] Filed:Apr. 14, 1972 [21] Appl. No.: 244,054

[30] Foreign Application Priority Data Apr. 16, 1971 Switzerland 5947/71Aug. 30, 1971 Switzerland 12683/71 [52] US. Cl. 177/210, 235/151.33 [51]Int. Cl. G0lg 3/15, G01g 23/42 [58] Field of Search 177/210, 2, 3, 25,DIG. 1,

l77/DIG. 3; 235/l5l.33

[56] References Cited UNITED STATES PATENTS 3,035,648 5/1962 Williams;177/210 X 3,063,635 11/1962 Gordon.... 177/210 X 3,366,191 1/1968 Reidet al. 177/210 3,488,589 l/l970 Kintner l77/21OX 3,565,193 2/1971 Wirthv 177/210 X 3,565,194 2/1971 Engle et al l77/2l0 X 3,684,875 8/1972Smith et al 235/l5l.33

Primary ExaminerRichard B. Wilkinson Assistant ExaminerStanley J.Witkowski Attorney, Agent, or Firm-Lawrence E. Laubscher [5 7] ABSTRACTForce-measuring apparatus of the type including electromagneticcompensation means having a movable member that is returned to a no-loadposition relative to a stationary member by the supply of compensatingcurrent pulses of constant amplitude and variable length to acompensation coil secured to said movable member, characterized by theprovision of counter means for counting subtotal numbers of countingpulses during periods corresponding with the lengths of saidcompensating current pulses, respectively, and means including countercontrol means for periodically transferring to store means the totalvalue of the successive subtotals in the counter means and forsimultaneously resetting the counter means to zero. Coarse control meansare provided for causing the totalized subtotal pulse count tocorrespond with a decimal multiple or fraction of a weight unit, andadditional store means are provided for optionally indicat ing for eachof a series of subtotal measuring operations the net arithmeticdifference between the totalare operable in conjunction with theoperation of said rate switch selection switch means for supplying thecounting pulses to corresponding low and high stages, respectively, ofthe counter.

9 Claims, 4 Drawing Figures PATENTEDJAHZZIUM sum 1m 4 mmhzEm Hun OmmN mmww PATENTED JAN 2 21974 SHEET 3 OF 4 mwm a mczcsou mwm a 250 =00cosusuwo 2Q r 29G mcrfimowz This invention relates generally to an'imp'ied' force-measuring apparatus, such as a balance, having totalizermeans for indicating the net sum of a plurality of periodic subtotalmeasuring operations.

It has been previously proposed-as evidenced, for example, by the priorUS. application Ser. No. 222,960 filed Feb. 2, 1972 in the name of PeterKunz-to provide a force-measuring apparatus of the type in whichdisplacement of a movable member from an initial no-load positionrelative to a stationary member in accordance with the magnitude of anapplied force controls by means of an electrical position sensing meansa current which is supplied to an electromagnetic compensation means tocounteract the.movement. The current is supplied to the compensationmeans in the form of constant amplitude pulses the lengths of which varyin a given relationship with the particular magnitude of the force, thelengths of said compensation pulses being counted by means ofhighfrequency counting pulses which actuate a counter,

thereby supplying a digital measuring result.

Generally the known measuring devices are so designed that in each casea single current pulse which compensates the force is counted by meansofc ounting pulses of constant frequency, and the resulting sum isrepresented as the measuring result. It has been foundthat thisarrangement suffers from a number ofdisadvantages.

Thus, for example, resolution is directly limitedby the frequency of thecounting pulse generator, for experiod. The frequency of the oscillatorcannot be inposition of equilibrium, thereby causing the system tobecome unstable.

It has also been found that random errors can falsify the measuringresult, owing to short-duration interfer ence vibrations. Suchvibrations can seldom be com-l pletely eliminated. In the case of theabove apparatus,

such vibrations therefore have a particularly disadvantageous effect onthe precision and reproducibility of the results, as the errors cannotbe corrected out owing, to the short measuring period. The presentinvention 2 was developed to avoid the above and other drawbacks of theknown force-measuring devices.

A primary object of the present invention is to provide an improvedforce-measuring apparatus including electromagntic compensation means ofthe type wherein the lengths of the compensation current pulses vary inaccordance with the extent of displacement of a movable member from itsinitial no-load position by the application of force thereto,characterized in that subtotals of the counting pulses which correspondwith I the lengths of said compensating current pulses are periodicallycounted by counter means, which subtotalsv are totalized and transferredto store means.

Preferably the totalizing means comprise one or more frequency dividersconnected with the output terminal of an oscillator for producing asignal of lower frequency then the oscillator, and a counter controlwhich is supplied with control pulses both from the frequency dividermeans and the oscillator.

In accordance with a more specific object of the invention, means arealso provided for adjusting the relationship between the weight value ofan individual counting pulse and the number of totalized individualresults, whereby the representation of the measuring result is indecimal multiples of weight units. In addition to at least one frequencydivider, such adjusting means are preferably in the form of anadjustable constant current generator for supplying the compensationcurrent pulses.

in accordance with a further object of the invention, indication and /orevaluation means are provided for representing the digital measuringresult, which means are. so designed as to afford an indication of allbut the last decimal of the sum of the counting pulses. Consequently, afurther weakness of previously proposed arrangementsnamely instabilityof indication of the last place (in the case of decade transfer, therespective last places)-is substantially eliminated, since because ofthe large number of counting pulses per weight unit, the apparatusaccording to the invention nonetheless produces a resolution of theindication which is at least as great as inthe previous arrangements.

Another disadvantage of previous arrangements is that they do not permitan initialloading (in'the case of balances, the tare) to be taken intoaccount electrically. Accordingly, use thereof on beam-less devices(such as for example pot balances, in which the dead weight of thesystem cannot be compensated by a counter weight as in the case of beambalances) was only possible when mechanical dead weight compensation,forexample by means of springs, was provided. In accordance with anotherfeature of the present invention, this last mentioned disadvantage isovercome in that means are also provided which, in consecutive measuringoperations, selectively indicate the overall total or the difference ofthe part totals. These means preferably substantially comprise aforward-reverse logic means associated with the counter, zero detectormeans, and a further storage means, each of said means receiving theircontrol orders fromthe counter eontrol.

Other objects and advantages of the invention will become apparent froma study of the following specification when-viewed in the light of theaccompanying drawing in which:

FIG. I illustrates schematically in block diagram form the electricalsystem of the present invention as used in connection with a pot typebalance;

FIG. 2 is an alternate embodiment of the electrical system of FIG. 1;

FIG. 3 is a voltage/time diagram illustrating the operation of themodulator means for varying the lengths of the constant amplitudecompensating current pulses, together with the resultant coil currentand counting current pulses; and

FIG. 4 is a detailed electrical block diagram of the counter controlmeans of FIG. 2.

Referring first more particularly to FIG. 1, the force measuringapparatus 1 is of the conventional pot magnet typeincluding a stationaryhousing 2 that is closed on all sides except for the necessary aperturesfor the tion current pulse and the number of corresponding ported by wayof a base 4 on a fixed support surface. Arranged with clearance in anannular air gap 5 between the housing 2 and the permanent magnet 3 is anannular coil 6 for producing the compensation force. The annular coil 6is fixedly connected to the movable member 7, which in turn isresiliently connected with the housing 2 by two substantially roundspring members 8. The upper end of the movable portion 7 comprises aweighing pan 9 for carrying material to be weighed. Two annularvertically spaced capacitors 11 which are fixedly connected to thehousing 2 form in conjunction with the movable portion 7 the mechanicalpart of the position sensing means.

In any weighing operation, the annular coil 6 is supplied with directcurrent by a constant current source 10 until the movable portion7,'which has been deflected out of the zero no-load position under theinfluence of the load of material to be weighed on the pan 9, has beenreturned to said no-load position. The output signals of the annularcapacitors 11 are converted in a transmitter circuit 12 and passed intosignal shaping means 13 to produce a control voltage Vc (FIG. 3) that isapplied to a pulse length modulator 14, as illustrated in FIG. 3. Thepulse length modulator is, per se,

well known in the art, as taught, for example, by the Naydan et al. US.Pat. No. 3,028,550, among others. The control voltage Vc is comparedwitha sawtooth voltage produced by the sawtooth generator means 16 includinga first frequency divider, which sawtooth voltage periodicaly rises fromzero at the moment T to a maximum value at the moment T, the maximumvalue corresponding at least to the weighing frame. During the initialperiod from T to T (i.e., the time period t in FIG. 3) when the sawtoothvoltage increases from zero to the control voltage V switch 17 is in afirst position in which compensation current is passed from the constantcurrent source 10 through the annular coil 6 by means of the pulselength modulator 14. After the sawtooth voltage in the pulse lengthmodulator 14 has increased to the value of the load-dependent controlvoltage V switch 17 is actuated to connect current source 10 with dummyload 18, so that during the remaining time from T to T all the currentfrom source 10 is switched over to the dummy load 18. The oscillatoralso supplies a reversible (i.e., up-down") counter with high-frequencycounting pulses via a gate 19 that is controlled by the pulse lengthmodulator 14 in such a way that it opens at the moment T (when currentbegins to flow to the annular coil 6), and is closed again after thetime t (when current is passed to the dummy load 18). Thus, the counter20 is supplied with counting pulses only during the duration of thecompensation current pulses. Flip-flop means 24 arranged between thepulse length modulator 14 and the switch 17 carries out thesynchronization function in such away that when there is coincidencebetween the control voltage and the sawtooth voltage in the pulse lengthmodulator 14, it receives a switch-over release signal, althoughswitching over will only occur after termination of the input of thecounting pulse just coming from the oscillator 15. Consequently, theswitching operation, which is always synchronized to the same flank ofthe respective counting pulse, provides optimum coincidence between thelength of the compensacounting pulses.

In the prior measuring systems, the measured result is transferred fromthe counter 20 at the given moment T, directly to indication storagemeans 21 and represented for digital reading by a visible indicationdevice 22 (Nixie tubes), or by printed read-out afforded by 1 printingmeans 23. In the present invention, on the other hand, means including afurther frequency divider 25 and counter control means 26 are providedfor effecting a plurality of individual subtotal weighing operations thetotal pulse sum of which is then transferred to store means 21, as willbe explained in detail hereinafter in a numerical example.

The oscillator 15 supplies counting pulses at a fre-- quency of 1 MHz,which, are supplied at that frequency to the gate 19 and, while the gate19 is open, to the counter 20. The first frequency divider of thesawtooth generator means 16 reduces the frequency in a ratio of 112,000,so that every 2 ms (interval between pulses) the pulse length modulator14 receives a pulse which in each case (a) opens the gate to the counter20, and (b) connects the current source 10 through the switch 17 to theannular coil 6 and (c) starts a new rise of the sawtooth voltage (momentT Therefore each individual weighing operation lasts 2 ms, in each casecurrent flowing and pulses being counted only for the portion of time 1(maximum 2 ms) which corresponds to the particular load to .be weighed.

Connected with the output terminal of the first frequency divider of thesawtooth generator means 16 is a second frequency divider 25 which againreduces the frequency, this time in a ratio of 1:200. The countercontrol 26 therefore receives a pulse every 0.4 s, which causes theparticular condition of the counter 20 at that moment to be transferredto the indication storage means 21 and also simultaneously causes thecounter 20 to be set to zero, ready for the next counting operation.Therefore 200 individual subtotal results are totalized to indicate theweighing result. The number of counting pulses corresponding to thistotal is illustrated in the indication means 22, the last decimal placebeing omitted. This produces the advantageous result that the influenceof interference vibrations are virtually elimi nated by determining anaverage. Furthermore, there is also no longer any danger that erroneousmeasuring results caused by the settlement time of the balance (about0.1 s) can appear in the indication. Finally, at least one furtherdecimal place is obtained in the digital representation of the weight.

Another substantial advantage of the above described arrangement lies inthe stability of indication. By using the total of counting pulses from200 individual weighing operations, depending on the selectedparameters, there are from 10 to 10" counting pulses available, so thatif only the last (unstable) decimal place is to be excluded from theindication of the weight, there still remains a resolution of from 10"to 10'.

The above mentioned parameters are: current strength of the constantcurrent source 10, frequency of the oscillator 15, reduction ratios ofthe frequency dividers l6 and 25, and the weighing range represented bythe maximum value (Vm) of the sawtooth voltage in the pulse lengthmodulator 14. Added to this, further means may be included in thecounter control 26 for suppressing given multiplies of pulses (forexample,

each third or each eighth counting pulse) so that the counter 20 countsa correspondingly reduced number of pulses. By adjusting theseparameters, coarse calibration of the counting pulses can be effected insuch a way that an indicated pulse approximately corresponds to adecimal multiple or fraction of a weight unit. In order to achieveprecise coincidence (fine calibration), the-constant current generator10 is made adjustable such that the current strength (amplitude of thecompensation current pulses) can be varied by a maximum of i 5 percentfrom the rated value. This adjustability offers the further advantagethat the balance can be adapted by adjustment to local fluctuations inacceleration due to gravity.

In accordance with another important feature of the invention, means maybe provided for weighing operations with tare and for taking intoaccount the dead load of the system. Connected in parallel with theindication storage means 21 is a tare storage means 27, and alsoprovided is a conventional bistable logic circuit 28 (for example, aflip-flop device as shown in the patents to Clement et al. No. 3,545,284and Reid et al. No. 3,366,191), a tare switch 26a which can be actuatedby hand and which is connected with the counter control 26, and a zero(i.e. null) detector 29 (as indicated, for example by the I-Iobel et al.Pat. No. 3,372,579). For carrying out weighing operations with tare,after actuating the'tare switch 26a the weight value ascertained fromthe taring operation is also introduced in the tare storage means 27. Insubsequent weighing operations, the value of the tare storage means 27is initially introducedinto the counter 20, whereupon theforward-reverse logic circuit 28 causes the counter 20 to countbackwards (that is to say, the counting pulses which enter it aresubtracted from the tare value) until the zero detector 29 signals thatzero has been reached. This signal passes to the forward-reverse logiccircuit 28 which then causes the counter 20 to count in the forwarddirection again.

If no additional material to be weighed is laid on the weighing pan 9,as many pulses pass into the counter 20 as are stored in the tarestorage means27; at the end of a measuring cycle of 0.4 s, the counter20 has therefore reached zero and this result is stored in theindication storage means 21 and passes into the indication means 22 andto the printing means 23.

If however further material is laid on the weighing pan 9 (orremoved'therefrom) more (or less, respectively) counting pulses passinto the counter 20 than are stored in the tare storage means 27. Theexcess (or the deficit, respectively) is passed into theindicationstorage means 21 at the end of the measuring cycle, andindicated for the duration of the next measuring cycle. It should benoted that the above described arrangement causes the particular resultto appear in the indication means 22 with a right sign with its realvalue. For example a surplus of 315 g (being the weight of additionalmaterial on the pan 9) is indicated as 0315, while a removal of weightis not indicated as a complement, as in the previously knownarrangements, but. for example when 3 l 5 g is removed, as 3 1 5 Thecorrect sign is also derived from the forwardreverse logic circuit 28.

it is quite obvious that by repeated actuation of the tare switch 26a,it is thus also possible to weigh a plurality fo components, with arespective indication of each net excess.

The dead load of the balance can also be taken into account in the abovedescribed manner. By actuating the tare switch 26a, for example at thebeginning of a series of net weighing operations, the value of theweight of the dead load is eliminated from the weight indication. Withthis arrangement it is also possible to reset the zero point of thebalance at any time if required, by redetermining the dead load simplyby actuating the tare switch 26a.

The above described apparatus is suitable not only for individual andseries measurements in rapid succession (weighing time of about 0.5 s),but also for determining weights which vary with time; in the lattercase, automatically registering devices can be connected to theapparatus in known manner. Obviously the invention can be generallyapplied to other kinds of electromagnetically compensating balances, forexample with balance beams, and also to corresponding forcemeasuringapparatuses.

The internal logic circuitry of the counter 20 and the counter controlmeans 26 is shown in FIG. 4. It will be seen that counter 20 is ann-stage counter having up and down input terminals connected with thegate 19 and the up-down logic means 28, a borrow output connected withthe zero detector 29, a data input connected with the tare store means27, reset and load counter inputs connected with the counter controlmeans 26, and an output terminal connected with the store means 21 andthe tare store 27. The borrow, counter up, counter down, load displayand load counter operations relative to the sawtooth waveform inputsignal to the modulator 14 are illustrated in FIG.

FIG. 2 illustrates an advantageous alternative form of the electricalcircuitry of the apparatus according to the invention. The arrangementdiffers from that shown in FIG. 1 in that the frequency divider 25 hastwo outputs 31 and 32 which are selectively connected by way of afrequency selection switch 33 to an input of the counter control 26. Thetwo outputs 31 and 32 respectively correspond to a reduction of 1:200 or1:20, respectively; that is to say, every 0.4 or every 0.04 sec.,respectively, the counter control 20 will receive a control pulse (thefrequency of the oscillator 15 is l MI-lz, the frequency divider 16reduces that in the ratio 1:2,000, and therefore supplies a pulse to thefrequency divider 25 every 2 ms). This control pulse causes theparticular condition of the counter 20 at receipt of the pulse to betransferred to the indication storage means 21 (and, if desired, to thetare storage means 27) and to the indication means 22.

The output of the gate 19 can be selectively connected by way of a stageswitch 30 to one of two inputs 34 or 35 of the counter 20. The input 34passes the counting pulse to the last (lowest) counting stage, while theinput 35 acts upon the next higher counting stage.

The two switches 30 and 33 can be switched by hand and are mechanicallycoupled (not shown) in such a way that when a divider output 31 or 32 isoperative the respective counting stage 34 or 35 is actuated. Thereforein an extended measuring cycle, after 200 individual measuringoperations a measuring result is obtained with a resolution which ishigher by a decimal power than that obtained in a shorter measuringcycle after 20 individual measuring operations.

Instead of two selectable measuring cycles as described above it wouldalso be possible, if required, to

provide three such cycles, that is to say there would be three differentoutputs at the frequency divider 25, three inputs at the counter 20 andcorrespondingly three positions of the switches 30 and 33.

The above described alternative embodiment with selectable duration ofthe measuring cycles makes it possible, with the same apparatus to carryout both precise measurements with a high degree of resolution and alsoless precise measurements with a lower degree of resolution. The lattercase occurs for example when material to be weighed is to be weighed-inor roughly weighed. With this alternative embodiment it is possible onthe one hand to carry out substantially more measuring operations perunit of time, when the precision and resolution of the measuring resultis not so very important, and on the other hand, by simply switchingover the duration of the measuring cycle, the device can be set into adifferent operating condition in which, after a correspondingly longermeasuring time, it supplies more accurate results whose resolution ishigher for example by a tenth power.

The above described force measuring apparatus thu has a resolution whichin comparison with the previously proposed apparatus is less dependenton the duration of the individual measuring periods and the frequency ofthe counting pulses, and which is also capable of substantiallyeliminating the influence of shortduration vibrations by averaging anyerrors resulting from the corresponding interference oscillations of themovable portion, resulting in a better degree of precision andreproducibility of the measuring results.

While in accordance with the provisions of the Patent Statutes thepreferred forms and embodiments of the invention have been illustratedand described, it will be apparent that various changes andmodifications may be made without deviating from the inventive concepts.

What is claimed is: l. Weighingapparatus, comprising a. a stationarymember including means defining a stationary magnetic field; b. amovable member normally having an initial noload position relative tosaid stationary member; c. electromagnetic compensation means operableupon the application to said movable member of a weight to be measuredfor returning said movable member to said no-load position, saidcompensation means including l. compensation coil means mounted on saidmovable member,.and I 2. means for supplying to said compensation coildirect-current pulses of constant height and of a length thatcorresponds with the instantaneous extent of displacement of saidmovable member from said no-load position, thereby to establish in saidcompensation coil means a restoring magnetic field relative to saidstationary magnetic field, said pulse supplying means including a.position detecting means for generating a dis placement signal themagnitude of which corresponds with the extent of displacement of themovable member from the no-load position; b. means including anoscillator and a first frequency divider for generating a sawtoothvoltage of a relatively high frequency;

6 0. means including normally-open switch means operable to connect asource of direct current with said compensation coil; and

d. pulse length modulator means for periodically closing said switchmeans for periods of time that correspond with the magnitude of saiddisplacement voltage relative to the instantaneous magnitude of saidsawtooth voltage;

d. pulse counter means;

e. gate means operable by said pulse length modulator means forsupplying counting pulses from said oscillator to said counter meansduring the periods of time said switch means is closed by said pulselength modulator, whereby said counter means continuously totalizes saidpulses;

. counter pulse storage and display means; and

. means for periodically transferring to said storage and display meansthe instantaneous totalized value of the pulses in said counter means,said transfer means including 1. second frequency divider meansconnected with said first frequency divider means for producing transferpulses of a relatively low frequency, and

2. counter control means operable by said low frequency transfer pulsesfor transferring the totalized condition of said counter means to saidstorage and display means and for resetting said counter to zero.

2. Apparatus as defined in claim 1, and further including coarse andfine calibration means for so adjusting the weight value of anindividual counting pulse relative to the number of totalized individualresults as to effect representation of the measured result as a decimalmultiple of a weight unit.

3. Apparatus as defined in claim 2, wherein said fine calibration meanscomprises means for adjusting the amplitude of the compensating currentpulses produced by said constant current source.

4. Apparatus as defined in claim 2, wherein said coarse calibrationmeans includes means associated with said counter control means forsuppressing each I of a given multiple of said counting pulses.

5. Apparatus as defined in claim 1, and further including indicatingmeans connected with said store means for providing a visible indicationof all but the last decimal place of the total pulse count contained insaid store means.

6. Apparatus as defined in claim 1, wherein said pulse counter isreversible; and further including h. tare storage means;

i. tare switch means for initially storing in said tare storage means anumber of pulses that corresponds with the tare weight;

j. means operable upon initial activation of said counter means fortransferring the tare pulses from said tare store means to said counter;

k. forward-reverse logic means for causing said counter to initiallyoperate in the reverse direction to subtract the weight pulses from thetare pulses; and

l. zero detector means operable when the number of tare pulses in thecounter has been reduced to zero for causing the forward-reverse logicmeans to reverse the counting direction of said counter, whereby saidcounter again counts in the forward direction.

7. Apparatus as defined in claim 1, wherein said totalizing meansincludes rate selection switch means for alternately selecting first andsecond rates at which the subtotal counting operations are performed.

supplying said counting pulses to that stage of said counter means thatcorresponds with the rate of subtotal counting operations selected bysaid rate selection switch means, respectively.

1. Weighing apparatus, comprising a. a stationary member including meansdefining a stationary magnetic field; b. a movable member normallyhaving an initial no-load position relative to said stationary member;c. electromagnetic compensation means operable upon the application tosaid movable member of a weight to be measured for returning saidmovable member to said no-load position, said compensation meansincluding
 1. compensation coil means mounted on said movable member, and2. means for supplying to said compensation coil direct-current pulsesof constant height and of a length that corresponds with theinstantaneous extent of displacement of said movable member from saidno-load position, thereby to establish in said compensation coil means arestoring magnetic field relative to said stationary magnetic field,said pulse supplying means including a. position detecting means forgenerating a displacement signal the magnitude of which corresponds withthe extent of displacement of the movable member from the no-loadposition; b. means including an oscillator and a first frequency dividerfor generating a sawtooth voltage of a relatively high frequency; c.means including normally-open switch means operable to connect a sourceof direct current with said compensation coil; and d. pulse lengthmodulator means for periodically closing said switch means for periodsof time that correspond with the magnitude of said displacement voltagerelative to the instantaneous magnitude of said sawtooth voltage; d.pulse counter means; e. gate means operable by said pulse lengthmodulator means for supplying counting pulses from said oscillator tosaid counter means during the periods of time said switch means isclosed by said pulse length modulator, whereby said counter meanscontinuously totalizes said pulses; f. counter pulse storage and displaymeans; and g. means for periodically transferring to said storage anddisplay means the instantaneous totalized value of the pulses in saidcounter means, said transfer means including
 1. second frequency dividermeans connected with said first frequency divider means for producingtransfer pulses of a relatively low frequency, and
 2. counter controlmeans operable by said low frequency transfer pulses for transferringthe totalized condition of said counter means to said storage anddisplay means and for resetting said counter to zero.
 2. means forsupplying to said compensation coil direct-current pulses of constantheight and of a length that corresponds with the instantaneous extent ofdisplacement of said movable member from said no-load position, therebyto establish in said compensation coil means a restoring magnetic fieldrelative to said stationary magnetic field, said pulse supplying meansincluding a. position detecting means for generating a displacementsignal the magnitude of which corresponds with the extent ofdisplacement of the movable member from the no-load position; b. meansincluding an oscillator and a first frequency divider for generating asawtooth voltage of a relatively high frequency; c. means includingnormally-open switch means operable to connect a source of directcurrent with said compensation coil; and d. pulse length modulator meansfor periodically closing said switch means for periods of time thatcorrespond with the magnitude of said displacement voltage relative tothe instantaneous magnitude of said sawtooth voltage; d. pulse countermeans; e. gate means operable by said pulse length modulator means forsupplying counting pulses from said oscillator to said counter meansduring the periods of time said switch means is closed by said pulselength modulator, whereby said counter means continuously totalizes saidpulses; f. counter pulse storage and display means; and g. means forperiodically transferring to said storage and display means theinstantaneous totalized value of the pulses in said counter means, saidtransfer means including
 2. counter control means operable by said lowfrequency transfer pulses for transferring the totalized condition ofsaid counter means to said storage and display means and for resettingsaid counter to zero.
 2. Apparatus as defined in claim 1, and furtherincluding coarse and fine calibration means for so adjusting the weightvalue of an individual counting pulse relative to the number oftotalized individual results as to effect representation of the measuredresult as a decimal multiple of a weight unit.
 3. Apparatus as definedin claim 2, wherein said fine calibration means comprises means foradjusting the amplitude of the compensating current pulses produced bysaid constant current source.
 4. Apparatus as defined in claim 2,wherein said coarse calibration means includes means associated withsaid counter control means for suppressing each of a given multiple ofsaid counting pulses.
 5. Apparatus as defined in claim 1, and furtherincluding indicating means connected with said store means for providinga visible indication of all but the last decimal place of the totalpulse count contained in said store means.
 6. Apparatus as defined inclaim 1, wherein said pulse counter is reversible; and further includingh. tare storage means; i. tare switch means for initially storing insaid tare storage means a number of pulses that corresponds with thetare weight; j. means operable upon initial activation of said countermeans for transferring the tare pulses from said tare store means tosaid counter; k. forward-reverse logic means for causing said counter toinitially operate in the reverse direction to subtract the weight pulsesfrom the tare pulses; and l. zero detector means operable when thenumber of tare pulses in the counter has been reduced to zero forcausing the forward-reverse logic means to reverse the countingdirection of said counter, whereby said counter again counts in theforward direction.
 7. Apparatus as defined in claim 1, wherein saidtotalizing means includes rate selection switch means for alternatelyselecting first and second rates at which the subtotal countingoperations are performed.
 8. Apparatus as defined in claim 7, whereinone of said rates of counting operations is a decimal multiple of theother.
 9. Apparatus as defined in claim 8, wherein said counter meansincludes a plurality of decimal stages, and further including stageselection switch means for supplying said counting pulses to that stageof said counter means that corresponds with the rate of subtotalcounting operations selected by said rate selection switch means,respectively.